Electrospun scaffolds of segmented polyurethanes based on PEG-PLLA-PTMC

R.B. TRINCA; M.I. FELISBERTI; G.A. ABRAHAM

Rosario

Congreso; VIII Congreso Latinoamericano de Órganos Artificiales, Biomateriales e Ingeniería de Tejidos (VIII COLAOB); 2014

SLABO

Polyurethanes (PU) are an important and versatile class of polymers characterized by a broad spectrum of compositions, molecular architectures, properties and applications. The chemical nature, structure and content of diisocyanates, polyols and chain extenders allow controlling the PU properties. By choosing all bifunctional compounds, linear block copolymers, named segmented polyurethanes (SPU), are obtained. A set of SPU based on low-molecular mass (2 kDa) poly(ethylene glycol) (PEG), poly(l-lactide) (PLLA) and poly(trimethylene carbonate) (PTMC), was synthesized. PLLA and PTMC homopolymers were obtained by ring-opening polymerization (ROP) from l-lactide and trimethylene carbonate monomers, using 1,4-butanediol as initiator. For SPU synthesis, a single vessel methodology with two reaction steps was adopted, a pre-polymer synthesis using 1,6-hexane diisocyanate followed by a pre-polymer extension using 1,4-butanediol. All SPU were characterized in terms of thermal and mechanical properties, composition and morphology. A wide range of compositions (between PEG, PLLA and PTMC) were investigated. Mechanical and thermal properties, as well as swelling degree, are shown to be directly related to the composition for all bi- and tri- component SPU. PLLA takes the major contribution in means of dimensional stability and mechanical properties, PTMC content lead to elastomeric behavior and enhance of mechanical properties, while PEG  is responsible for the hydrophilicity  of SPU, which are related to mechanisms of cell adhesion. Selected formulations of SPU (e.g. 10 % PEG, 60 % PLLA and 30 % PTMC, SPU-10-60-30) were subjected to electrospinning processing seeking the obtaining of fibrous scaffolds for tissue engineering applications. A typical electrospinning setup consisting of a high-voltage power supply, a single nozzle and a static flat collector, was used. Electrospun micro/nanofibrous structures with fiber diameter ranging from 650 nm to up micrometric dimensions were obtained by varying the applied voltage, needle tip-to-collector distance and flow rate. Mechanical and thermal properties shown to be dependent on either the SPU films were obtained by solvent cast or electrospinning, glass transition relaxation events of electrospun or solvent casted films of the SPU-10-60-30 presents no significant variation in meanings of temperature range, while the magnitude of such transitions present some level of variation. In mechanical meanings, electrospun films are softer and show an elastomeric behavior and stretching recovery. In order to study the influence of the nanofibrous surface on cell adhesion and proliferation, cell viability assays are under progress.